Chapter 11

Backup facility

A DBMS COPY utility that produces a backup copy (or save) of an entire database or a subset of a database.

Information repository

A component that stores metadata that describe an organization's data and data processing resources, manages the total information processing environment, and combines information about an organization's business information and its application portfolio.

Information Resource Dictionary System (IRDS)

A computer software tool that is used to manage and control access to the information repository.

After image

A copy of a record (or page of memory) after it has been modified.

Before image

A copy of a record (or page of memory) before it has been modified.

Checkpoint facility

A facility by which a DBMS periodically refuses to accept any new transactions. The system is in a quiet state, and the database and transaction logs are synchronized.

Data administration

A high-level function that is responsible for the overall management of data resources in an organization, including maintaining corporate-wide definitions and standards.

Database change log

A log that contains before and after images of records that have been modified by transactions.

Deadlock prevention

A method for resolving deadlocks in which user programs must lock all records they require at the beginning of a transaction (rather than one at a time).

Locking

A process in which any data that are retrieved by a user for updating must be locked, or denied to other users, until the update is completed or aborted.

Heartbeat query

A query submitted by a DBA to test the current performance of a database or to predict the response time for queries that have promised response times. Also called a canary query.

Data dictionary

A repository of information about a database that documents data elements of a database.

Database administration

A technical function that is responsible for physical database design and for dealing with technical issues, such as security enforcement, database performance, and backup and recovery.

Exclusive lock (X lock, or write lock)

A technique that prevents another transaction from reading and therefore updating a record until it is unlocked.

Forward recovery (rollforward)

A technique that starts with an earlier copy of a database. After images (the results of good transactions) are applied to the database, and the database is quickly moved forward to a later state.

Aborted transaction

A transaction in progress that terminates abnormally.

Deadlock resolution

An approach to dealing with deadlocks that allows deadlocks to occur but builds mechanisms into the DBMS for detecting and breaking the deadlocks.

Journalizing facility

An audit trail of transactions and database changes.

Deadlock

An impasse that results when two or more transactions have locked a common resource, and each waits for the other to unlock that resource.

Inconsistent read problem

An unrepeatable read, one that occurs when one user reads data that have been partially updated by another user.

Authorization rules

Controls incorporated in a data management systems that restrict access to data and also restrict the actions that people may take when they access data.

Database recovery

Mechanisms for restoring a database quickly and accurately after loss or damage.

Database security

Protection of database data against accidental or intentional loss, destruction, or misuse.

Backward recovery (rollback)

The backout, or undo, of unwanted changes to a database. Before images of the records that have been changed are applied to the database, and the database is returned to an earlier state. Rollback is used to reverse the changes made by transactions that have been aborted, or terminated abnormally.

Encryption

The coding or scrambling of data so that humans cannot read them.

Database destruction

The database itself is lost, destroyed, or cannot be read.

Concurrency control

The process of managing simultaneous operations against a database so that data integrity is maintained and the operations do not interfere with each other in a multiuser environment.

Data archiving

The process of moving inactive data to another storage location where it can be accessed when needed.